Magnetron having evacuated discharge sub-assembly united with unevacuated magnetic and resonant cavity structure



Dec. 2l, 1965 G. A. KRUG, JR 3,225,249 MAGNETRON HAVING EVACUATED DISCHARGE SUB-ASSEMBLY UNITED WITH UNEVACUATED MAGNETIC AND RESONANT CAVITY STRUCTURE Filed April 27. 1962 2 Sheets-Sheet 1 GEORGE A.KRUG,JR. lr /VQHLSD' 2325 2a 22 BY HIS ATTORNEY.

Dec. 2l, 1965 G. A. KRUG, JR 3,225,249

MAGNETRON HAVING EVACUATED DISCHARGE SUB-ASSEMBLY UNITED WITH UNEVACUATED MAGNETIC AND RESONANT CAVITY STRUCTURE Filed April 27, 1962 2 Sheets-Sheet 2 INVENTORI GEORGE A. KRUG,JR.

United States Patent C) s 22s 249 MAoNnrnoN Havnsr; nvacnarnn nrscnanoa SUB-ASSEMBLY UNirnn wirr-1 UNavAcUArnn My invention relates to radio frequency apparatus and pertains more particularly to `new and improved voltage tunable magnetron packages incorporating new and irnproved combined bowl type magnet and R.F. structures and new and improved means for attenuating undesirable R.F. currents on D.C. supply leads for a voltage tunable magnetron tube mounted in such a package.

A voltage tunable magnetron package generally comprises a unitary structure including an RP. cavity circuit having an R.F. output and a voltage tunable magnetron tube securely mounted in t-he circuit, D.C. circuit means for applying appropriate operating potentials to the electrodes of the tube, and a magnet assembly providing an operating magnetic field for the tube. The magnet assembly generally comprises a permanent magnet having closely spaced opposed pole pieces defining a gap wherein the magnetic field is disposed and the magnetron tube is predeterminedly adjustively positioned relative to the field. Additionally, it is often desirable that the magnet assembly be of the bowl type, or, in other words, the type that is generally spheroidal, supports spaced coaxial pole pieces extending reentrantly therein, and is adapted for enclosing the mentioned magnetron tube and circuitry. However, in voltage tunable magnetron packages designed for operation in certain relatively low frequency ranges, such, for example, as the range of 50G-1200 mc. the R.F. circuitry would assume substantial proportions. This would result from the fact that such cavities must generally be of a size comparable to one-half wave length at the lowest operating frequency contemplated. Thus, a bowl magnet appropriately dimensioned to enclose such circuitry would be substantially large, heavy and expensive for many applications. Accordingly, in some applications the bowl magnet can be employed also to provide an oscillatory circuit impedance and thus obviate the need for a contained R.F. cavity. However, in voltage tunable magnetron packages wherein the tube incorporates an electron injection system it is desirable t provide for relative adjustments kof the tube and operating magnetic field, appropriate tube mounting including adequate R.F. coupling to a cavity defined by the magnet structure, and adequate dissipation of heat generated by the tube during operation. My lnventon contemplates an improved voltage tunable magnetron package utilizing the magnet structure in defining an R.F. cavity and improved means for enabling relative adjustable positioning of the tube and magnetic field. My invention also contemplates improved means for coupling R.F. energy from the apparatus which also serves effectively to maximize heat transfer externally from the tube to the magnet structure for dissipation thereby.

Further, means are generally required in voltage tunable magnetron packages to provide for adjustable positioning of the magnetron tube relative to the magnetic tield between the pole pieces of the magnet structure. My invention contemplates improved means for providing adjustive positioning of the operating magnetic iield involving means for holding the tube relatively fixed and adjustably altering the position of the magnetic lield relative to the tube.

Also, in lower power wide band operation of the discussed type of package, extremely low external Q is required to obtain the wide bandwith. To obtain low external Q, extremely heavy, or tight, R.F. output coupling is required. My invention contemplates improved means adapted for affording such tight R.F. output coupling and thus is adapted for effecting the low external Q required for wide bandwidth operation.

Still further, R.F. currents generally appear on the D.C. supply leads of voltage tunable magnetron packages as a result of tube external coupling and these currents are usually undesirable in that they cause external radiation and inevitably are reflected at some point, such as those points `at which the leads are connected to a power supply. The radiation is undesirable in that it can cause spurious signals and may necessitate the provision of appropriate shielding means. The mentioned reflection is undesirable in that it can result in alterations of the output spectrum of the device causing excessive power variations, tuning rate variations, or even holes over the band of frequencies covered. R.F. currents on the D.C. leads can also cause sensitivity to the physical positions of the leads which is very undesirable, especially under vibratory operating conditions. Thus, it is desirable that the R.F. currents be attenuated or eliminated close to the magnetron tube and preferably within a part of the package. Also, it is desirable that the means for accomplishing the attenuation not adversely affect the configuration of the magnetic field in the magnet gap, thereby to avoid adverse effects on tube operation. The present invention contemplates the provision of R.F. attenuating means adapted for accomplishing all these desiderata.

Accordingly, a primary object of my invention is to l provide new and improved voltage tunable magnetron package structures including new and improved combined magnet and R.F. circuit structures.

Another object of my invention is to provide a new and improved bowl type voltage tunable magnetron package adapted for low frequency, wide bandwidth operation.

Another object of my invention is to provide in -a voltage tunable magnetron package new and improved R.F. circuitry including new and improved means for enhancing heat dissipation.

Another object of my invention is to provide in a voltage tun-able magnetron package new and improved means for providing desired adjustive positioning of a magnetron tube in the package and an operating magnetic iield extending through the tube.

Another object of my invention is to provide a new and improved voltage tunable magnetron package adapted for wide bandwidth operation and including new and improved output coupling means adapted for affording a low external Q required for such operation.

Another object of my invention is to provide new and improved means for attenuating R.F. currents appearing on the D.C. supply leads of a voltage tunable magnetron package and which means is particularly adapted for avoiding adverse effects on the configuration of the operating magnetic lield extending through a magnetron tube in the package.

Another object of my invention is to provide a voltage tunable magnetron package of minimum size, weight and number of parts and thus adapted for wider applications, ease of assembly and reduced cost of manufacture.

Further objects and advantages of my invention will become apparent as the following description proceeds and the features of novelty which characterize my invention will be pointed out with particularity in the claims annexed to and forming part of this specification.

In carrying out the objects of my invention I provide a unitary package assembly including a bowl-type magnet subassembly comprising a pair of opposed dish-shaped permanent magnet segments secured together to define a generally spheroidal space. The magnet segments include coaxial apertures for having positioned therein reentrant coaxial pole pieces having spaced opposed inner ends deffining a gap. The inner ends of the pole pieces are adjustively positionable for adjustably positioning a rnagnetic field therebetween relative to the axis of the pole pieces. The internal surface of the magnet assembly also constitutes a resonant cavity for a voltage tunable magnetron tube and equatorially mounted in the cavity is an insulative support member having a voltage tunable magnetron tube rigidly mounted and positioned coaxially in the magnet gap therein. The tube includes longitudinally spaced anode contacts connected to anode circuitry in the tube envelope. Externally of the envelope each anode contact is connected to a respective magnetic pole piece by at least one, and preferably a plurality of circumferenvtially spaced, low inductance, high heat conductivity connections, thereby to provide R.F. connections between each side of the anode circuitry and the resonant cavity for completing an oscillatory circuit. Additionally, the inductances enhance heat transfer from the tube to the magnet structure for dissipation and are flexible to facilitate relative adjustive positioning of the pole pieces. Also provided is a coaxial RF. output including an inner conductor comprising an inductive loop having the inner ends supported by the insulative support member and conductively coupled to one of the anode contacts. The intermediate region of the inductive loop is generally U-shaped and conforms to the contour of the inner surface of the resonator in very close proximity thereto. Additionally, the intermediate region of the loop includes a attened section which affords a low impedance which is required for heavy coupling and a low external Q. D.C. leads from the D.C. contacts of the magnetron tube extend in spaced relation through an insulative member in a D.C. connector structure mounted in the side of the magnet assembly. Provided in the connector structure are a plurality of parallel non-magnetic elements characterized by resistive lossiness and adapted for attenuating R.F. currents in the leads.- Each attenuating element is formed vwith a spiral high-pitched groove in which a lead is Wound and substantially imbedded. The attenuating elements can advantageously comprise porous ceramic elements having carbon uniformly distributed therethrough. In a second embodiment the output coupler comprises a pair of parallel planar conductors constituting a line-over-ground plane transmission line which interconnects each anode contact with one of the conductors of a coaxial connector. The planar conductors are spaced parallel by the insulative support'member. Also, the insulative support member can include an electrically insulative thermally conductive insert immediately surrounding the tube and adapted for enhancing heat transferto the output means for in-k creasing heat dissipation.

For a better understanding of my invention, reference may be had to the accompanying drawing in which:

FIGURE l is a plan view of an embodiment of the present invention with the upper section of the magnet assembly removed and the R.F. output and D.C. connectors sectionalized;

FIGURE 2 is a sectional View of the embodiment of FIGURE 1 with the upper section of the magnet assembly in place and with the view taken along the lines 2f-2 in FIGURE l and looking in the direction of the arrows;

FIGURE 3 is a sectional view of a voltage tunable magnetron tube of a type employed in the presently disclosed package;

FIGURE 4 is a partially sectionalized view of the RF. attenuators for the D.C. leads illustrated in FIGURE l;

FIGURE 5 is a sectional view of another embodiment of my invention; and

FIGURE 6 is a fragmentary perspective view ot the RF. output structure illustrated in FIGURE 5.

Referring to FIGURES l and 2, there is shown a voltage tunable magnetron package generally designated 1 and including a bowl-type magnet subassembly 2 having a voltage tunable magnetron tube 3 mounted centrally therein. The magnet subassembly 2 is adapted for providing both a magnetic operating field extending generally coaxially through the tube and an external RF. cavity circuit for the tube.

The magnet subassembly 2 comprises an opposed pair of dish-shaped permanent magnet segments 4 each securely fitted in a die-cast non-magnetic mount or casing 5 which is also generally dish-shaped. The mounts or casings 5 can be advantageously formed of aluminum or any other low heat retentivity and high thermal conductivity material for enhancing heat dissipation. Additionally, the magnet subassembly can be provided With fastening means generally designated 6 to secure the described segments thereof together in the manner illustrated and to define an enclosed substantially spheroidal space therein generally designated 7. rl`he space is adapted for serving in the assembly to contain the voltage tunable magnetron 3 and to constitute a cavity circuit therefor. rI`his feature of the structure will be described in greater detail hereinafter.

Additionally, the magnet segments 4 and casings 5 are formed to include coaxial apertures in which are suitably rigidly tted coaxial pole pieces 8 formed preferably of a high permeability magnetic materialrsuch as soft iron and extending centrally in the space 7 with the inner ends in opposed spaced relation. Each pole piece 8 carries on the inner end thereof an adjustable inner pole piece 10 which inner pole pieces define a gap for having positioned therein the mentioned magnetron tube 3 and affording a magnetic field extending generally coaxially through the tube. The adjustive pole pieces 10 are adapted for being moved in Various planes by any suitable means (not shown) and can each comprise a section of a sphere having a planar surface 11 and a convex surface 12. The convex surfaces 12 can cooperate with concave surfaces 13 formed in the inner ends of the pole pieces 8. Thus, these elements can comprise ball-and-socket joints adapted for enabling the pole pieces 10 each to be independently adjustively positioned about various axes, thus to provide for adjustable positioning of the magnetic field between the pole pieces 10 relative to the tube 3. The structure involving inner pole pieces moveable in various planes including specifically the ball-and-socket arrangement illustrated is not part of the present invention but is disclosed and claimed in a concurrently filed copiending application S.N. 190,753, M. Bessarab, led April 27, 1962, assigned to the same assignee as the present invention.

Further, in accordance with the invention disclosed in and covered by the claims of U.S. Patent No. 2,939,046 of D. A. Wilbur, issued May 31, 1960, and assigned to the same assignee as the present invention, the presently disclosed structure can be provided with means for producing a magnetic field component parallel to the electric field in the magnetron tube 3, thereby to enhance stream control. In the presently disclosed structure this is accomplished by making one of the adjustable pole pieces 10 smaller than the other and whereby the field in the gap is barrelled or predeterminedly shaped to provide the desired magnetic field components extending parallel to the electric field in the magnetron tube 3.

The magnetron tube 3 can be of the type disclosed and claimed in U.S. Patent No. 2,930,933 of G. I. Griffin, Ir., et al., issued March 29, 1960, and assigned to the same assignee as the present invention. Such a tube is illustrated in section in FIGURE 3 to bring out the relative location of electrode contacts and thereby to facilitate the description and understanding of the RF. and D.C. circuit features of the present invention. Briefly, and

5, as illustrated in FIGURE 3, the tube 3 is constructed to include stacked alternate ceramic and metal elements. The ceramic elements generally include a plurality of cylindrical ceramic Wall sections 16 and an apertured disk-like ceramic end cap 17. The metal members are suitably brazed to or between opposed surfaces of the ceramic elements to complete a hermetically sealed evacuated envelope and include a metal end cap 18 carrying a cylindrical non-emissive cathode 19 extending centrally in a cylindrical space dened by a plurality of anode segments generally designated 20. The anode segments 20 are arranged in `a pair of interdigital sets, with each set being carried by a washer-like contact Z1. The contacts 21 are each sealed between a pair of ceramic cylinders 16 and are thus mutually insulated. A filamentary emitter 22 is suitably mounted on the ceramic end cap 17, with leads sealed therethrough and connected to a pair of button-like contact members 23 bonded to the outer surface of the ceramic end cap 17. A frustoconical control electrode 24 is sealedbetween one of the ceramic insulators 16 and the ceramic end cap 17 and is positioned about the emitter 22. By means of a lead not shown and which extends also in a sealed manner through the ceramic end cap an electrical connection is made between; the control electrode Z4 and another button-like contact member 25 bonded to the outer surface of the ceramic end cap.

As discussed above, the magnetron tube 3 is adapted for operating while generally coaxially aligned with the magnetic field extending beween the pole pieces 10 of the above-described magnet assembly. Additionally, the tube requires for operation the application of suitable DC. potentials to the various electrodes supplied through the metal end cap 1S and the contact buttons 23 and 25. These are provided through D C. leads generally designated 26 in FIGURE 1 and extending from the mentioned contacts through a suitable connector 27 which is mounted in the sidewall of the magnet assembly and will be described in detail hereinafter.

Provided for rigidly supporting the magnetron tube 3 coaxially in the magnet assembly and in the gap defined by the pole pieces 10 is an insulative support structure 30 extending transversely across the midsection, or equator, of the magnet assembly. As seen in FIGURES l and 2 the support structure 30 can comprise a pair of planar insulative elements 31 each formed with cooperating recesses adapting the elements 31 for fitting tightly about the ceramic section 16 of the tube positioned between the anode contacts 21 when the inner edges of the support elements are abutted as shown in FIGURE l. edges of the insulative elements 31 are rigidly itted in recesses 32 formed in the inner edges of the magnet segments 4 and thus the support structure 30 -is rigidly retained in the position illustrated. Additionally, the elements 31 are formed with a plurality of spaced weight reducing apertures 33. Thus, the support structure 30 is effective for holding the magnetron tube 3 rigidly supported in coaxial relation to the magnet assembly in the gap between the inner pole pieces 10 and the pole pieces 10 are adjustably positionable in various planes for predeterminedly adjustively positioning the magnetic field therebetween relative to the axis of the tube. This distinguishes the presently disclosed structure from prior arrangements such as that disclosed and claimed in copending U.S. application S.N. 736,867 of M. Bessarab, filed M-ay 31, 1958, and assigned to the same assignee as the present invention, now U.S. Patent No. 3,020,446, wherein the pole pieces are stationary and a cavity structure carrying a magnetron tube therein is adjustively positionable relative to the magnet thereby to eect predetermined y.adjusted positioning of the tube relative to the magnetic field between the pole pieces.

As mentioned above, in the presently disclosed structure the magnet assembly serves also as an external cavity for the tube 3. More specically, in the tube 3 the ad- The outer f jacent anode segments comprise capacitances for use in establishing a resonant circuit, and the inner wall of the magnet assembly, or cavity 7 is adapted for providing the inductance required to establish a resonant circuit. In order to interconnect the capacitances of the tube and the inductance of the cavity wall and thus establish the mentioned circuit, I have provided a plurality of circumferentially spaced, low-inductance connections 35 brazed to the surfaces of each of the anode contacts 21 on the tube and extending and brazed to the side surface of the adjacent inner pole pieces 10. In this arrangement therconnections 35 are preferably at strips of metal which are bowed outwardly and flexible to enable adjustive positioning of the pole pieces without adversely :affecting the required conductive connections made thereby between the anode contacts and pole pieces. Additionally, the connections 35 are preferably formed of a high heat conductivity material in order to'provide substantial thermal paths between the tube and pole pieces, thereby to enhance heat transfer to the exterior of the magnet assembly for dissipation thereby.

The connections 35 comprise the RF. circuit between the inductive internal wall of the magnet assembly and the capacitances provided in the tub 3, and when the tube 3 is operated the circuit is adapted for generating oscillations and establishing a standing electro-magnetic wave in the spheroidal space or cavity 7 defined by the magnet segments 4. Conductivity of oscillating currents on the internal wall of the cavity 7 can be facilitated by providing thereon a low-resistance coating 36 formed, for example, of copper, silver or any other suitable material.

In order to extract R.F. energy from the package I have provided a coaxial output generally designated 37 mounted rigidly in the side of the magnet assembly at the equator thereof. The output 37 includes a threaded outer conductor 38 conductively connected to the low resistance conductive coating 36 in the cavity. The inner conductor 39 of the output includes a large generally U-shaped, or bail-like, loop 4t) extending in a radial plane in the assembly and cooperating with the wall thereof to provide an output transmission line. The loop 4t? conforms generally and extends close to the R.F. current conducting surface of the assembly and includes an inner end which extends generally parallel to the axis of the assembly through an aperture in the support member and is securely conductively connected to a tab 41 on the upper one of the anode contacts 21. The intermediate section of the loop 4t), or that section which extends parallel to the bottom surface of the resonant cavity, is -attened, and which is between the angularly extending outer sections at each end thereof, or planar, to provide a low impedance which is required for effecting heavy coupling between the output and cavity. As mentioned above, the heavy coupling is required for obtaining a low external Q and an extremely low external Q is required for .affording wide bandwidth operation. Also, the portion of the output coupler immediately connected to the tube is effective for providing a capacitive load which effectively lowers the resonant frequency of the circuit and concentrates the electric lield at the magnetron tube which is desirable f-or optimum tube performance. Thus, the operating frequency of the present apparatus is not determined solely by the dimensions of the cavity but, instead, is determined principally by the capacitive loading arrangement. This is desired since in designing apparatus for various operating frequencies it is easier and preferable to alter the design of the capacitive loading than the cavity structure and also results in a minimum sized cavity.

As also mentioned above, D.C. connections to the tube 3 are required to provide satisfactory operating potentials on the several electrodes therein and, as a result of tube external coupling, RF. currents generally appear on the leads 26 making these connections. In order to remove these RF. currents and thereby avoid undesirable external radiation and reflections back to the tube I have provided and include an RF. attenuating structure. Specifically, in the present structure the D.C. leads 26 which are suitably secured to the cold cathode contact I8 and to the contact buttons 23 and 25 are made to extend through a D.C. connector generally designated27 which includes RF. attenuators constructed according to a feature of my invention. Internally of the cavity 7 the leads 26 extend through apertures in the support member 30. Thus, the support member 30 serves as a strain relief on the connections to the tube contacts. The connector 27 comprises a metal sleeve 43 having the inner end suitably secured in an aperture in the side wall of the magnet assembly and containing an insulative plug 44 which can be formed of a suitable potting compound if desired. The plug 44 houses a plurality of elongated parallel attenuator elements 45 corresponding in number to the number of D.C. leads.

As better seen in FIGURES l and 4, the leads 26 are bared of insulation from the points where they emerge from the apertures in the support member to the point on the outer side of the attenuator elements 45. Also, the elements 45 are each formed with a high-pitched spiral groove 46 extending the lengths thereof and having the bared section of the lead 26 wound in the groove. The wire diameter and groove depths are preferably such that the wires are essentially imbedded in the grooves. Expressed in another manner the dep-th of each groove is substantially greater than the diameter of the wire therein whereby the wire, when wound in the groove, is substantially imbedded in the element 45. Additionally, the elements 45 are formed of a non-magne-tic electrically lossy material. Preferably the elements 45 are formed of a porous ceramic made electrically lossy by the uniform distribution therethrough of carbon or any other material having comparable electrical properties. The lossiness of the elements 45 and the tight coupling between the leads 26 and the elements 45 afforded by the disposition of the leads in the spiral groove is effective for attenuating RF. currents tending to appear on the leads. Further, in order to insure such attenuations as close to the tube as possible and with no deleterious side effects to the tube performance, such as can result from disturbance of the operating magnetic field, the attenuating structure is predeterminedly dimensioned relative to the contemplated oper-ating frequencies of the package. Specifically, the length of each groove 46 is such that when a lead is wound therein a wavelength of developed lead at the lowest operating frequency contemplated is coupled to the lossy element 45 which thus insures dissipation of the undesired RF. current. This, it is to be noted, is accomplished with the element 45 being physically considerably less than one wavelength long which is desirable from the standpoint of minimizing dimensions of the elements employed. `It is to be noted fur-ther that the non-magnetic nature of the material of which the elements 45 are formed enables these elements to be closely positioned relative to the tube without concern about adversely affecting the operating magnetic field extending through the tube. With RF. currents thusly removed from the leads, relative motions lof the leads, such as may be encountered when the package is applied to equipment in vibrating vehicle, has little or no effect on the R.F. output spectrum.

Illustrated in FIGURES and 6 is a modified form of my invention which can be substantially identical to the embodiment of FIGURES 1 4 except for the output coupling arrangement. The elements of the structure of FIG- URES 5 `and 6 which can be substantially identical structurally and functionally to those of the device of FIG- URES 1 4 are identified by the same numerals as applied to FIGURES 1-4. Additionally, D C. leads (not shown) can also be provided with the R.F. attenuating means described above and illustrated in FIGURES 1 4.

The output coupling arrangement which represents the major difference of the embodiment 50 is perhaps better seen in FIGURE 6. Specifically, the output arrangement includes a coaxial connector 51 having the outer conductor 52 thereof secured in the sidewall of the magnet structure 2 and conductively connected to coating 36. In the cavity 7 defined by the magnet structure the outer conductor 52 is conductively connected to an upper plane contact member 53 which lies on the upper surface of the insulative tube support member 30 and includes an apertured end fitting around and making annular contact with the upper anode ring 21 of the tube 3, The inner conductor 54 of the coaxial connector 51 includes a down-turned inner end to which is conductively connected the outer end of a lower plane contact 55 which has a portion lying iiat against the under surface of the tube support member 30. The contact 55 includes an apertured inner end which fits around and makes annular electrical contacts with the lower one of the anode contacts 21 on the tube 3. In this arrangement the Contact member 55 is bent so that the inner apertured end lies in an appropriate plane to accommodate the positioning therein of the lower anode contact.

Also, in the presently disclosed embodiment the tiexible inductive straps 35, instead of being directly connected to the anode contact rings as in the first-described embodiment, are connected between the pole pieces 10 and appropriate ones of the output contact members 53 and 55 at the apertured portions which contact the anode rings. Further, in the presently disclosed embodiment there is provided a heat conductive, electrically insulative member 56 which lits about the tube 3 between the anode contacts 21 thereon. This member can comprise two elements adapted for completing a split annulus to enable assembly of the member 56 about the tube in the manner illustrated. The member 56 can be advantageously formed of boron nitride and yserves effectively in maximizing -heat transfer from the tube outwardly toward the straps 35 for conduction to the magnet assembly. Also, it serves effectively in maintaining appropriate spacing between the apertured ends of the contact members 53 and 5S.

In the embodiment of FIGURES 5 and 6 the plane contacts 53 and 55 constitute a line-over-plane output transmission line and determine the tuning bandwidth of operation of the package. However, the cavity 7 defined by the magnet structure determines the center frequency of operation. Thus, through the practice of my invention a voltage tunable magnetron package can be constructed by selecting a cavity-defining magnet having a predetermined resonance frequency and, thus, determining the center frequency of the package, and by dimensioning the line-over-plane output coupler to have a characteristic impedance suitable for obtaining a desired tuning bandwidth. Thus, in designing packages one parameter can be changed independently of the other and alterations of the determining bandwidth can be accomplished very simply by altering the dimensions of the line-overplane structure and thus altering the characteristic impedance thereof.

Additionally, the direct conductive coupling of the output to the tube anode circuit provides the above-discussed tight, or heavy, coupling desired for providing a low external Q and thereby effective for aording wide bandwidth operation.

While I have shown and described specific embodiments of my invention I do not desire my invention to be limited to the particular forms shown and described, and I intend by the appended claims to cover all modifications within the spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. Radio frequency apparatus comprising a magnet structure including a pair of opposed spaced pole pieces defining a gap, supporting means supporting said pole pieces for angular adjustment to vary the configuration of the magnetic field in said gap, retaining means carried by said magnet structure supporting an electric discharge device in a fixed position in said gap, said device including at least one external contact member, and means including at least one flexible conductive element interconnecting said contact member and one of said pole pieces to complete an R.F. circuit therebetween.

2. Radio frequency apparatus comprising a magnet structure including a pair of opposed spaced pole pieces defining a gap and an interconnecting conductive section, angular adjusting support means supporting said pole pieces to predeterminedly angularly position said pole pieces and thereby determine the configuration of the magnetic field in said gap, a magnetron tube fixedly mounted in said gap in spaced relation to said pole pieces, said tube including an anode circuit and an axially spaced pair of anode contacts, and means including at least one flexible electrically and thermally conductive element interconnecting each said contacts and an adjacent pole piece for enabling relative adjustive movements of said pole pieces, completing a radio frequency circuit through said magnet structure and providing thermal paths from 'said tube to said magnet structure.

3. Radio frequency apparatus comprising a magnet structure defining a radio frequency cavity and having a pair of opposed pole pieces defining a gap in said cavity, a support member extending transversely in said cavity and iixedly supporting a magnetron tube in said gap in spaced relation to said pole pieces, said tube including an interdigital anode circuit and an axially spaced pair of anode contacts, means including at least one low inductance electrically and thermally conductive element interconnecting each said contacts and an adjacent pole piece for completing a radio frequency circuit with said magnet structure for establishing a standing electromagnetic wave in said cavity and providing thermal paths from said tube to said magnet structure, and means for extracting radio frequency energy from said cavity.

4. Radio 'frequency apparatus comprising a magnet structure defining a radio frequency cavity and having a pair of opposed pole pieces defining a gap in said cavity, said pole pieces being predeterminedly adjustively positioned and thereby determining the configuration of the magnetic field in said gap, a magnetron tube including an envelope containing an anode circuit and carrying an axially spaced pair of anode contacts, an insulative member extending transversely across said cavity and supporting said tube in said gap in spaced relation to said pole pieces, means including a plurality of bowed lowinductance thermally conductive straps interconnecting each said contacts and an adjacent pole piece for enabling relative adjustive movements of said pole pieces, completing a radio frequency circuit with said magnet structure for establishing a standing electromagnetic wave in said cavity and providing substantial thermal paths from said tube to said magnet structure, and means for extracting radio frequency energy from said cavity.

5. Radio frequency apparatus comprising a magnet structure defining a radio frequency cavity and having a pair of opposed pole pieces defining a gap in said cavity, a magnetron tube mounted in said gap in generally coaxial relation with the magnetic field in said gap, connector means operatively connecting said tube to said cavity for establishing a standing electromagnetic wave therein, and radio frequency output coupling means for extracting energy from said cavity comprising a coaxial connector including an inductive loop defining a pair of outer sections and an intermediate section, said intermediate section having a substantial length thereof extending in close proximity to the interior surface of said cavity fr effecting tight coupling to said cavity.

6. Radio frequency apparatus according to claim 5, wherein said loop includes a planar section extending substantially parallel to a wall section of said cavity whereby low impedance desired for effecting heavy coupling between said output means and cavity is obtained.

7. Radio frequency apparatus comprising a magnet structure defining a radio frequency cavity and having a pairiof opposed pole pieces defining a gap in said cavity, a magnetron tube including an anode circuit and at least one external anode contact, an insulative member extending transversely across the interior of said cavity and supporting said tube in said gap, connector means interconnecting said tube and said pole pieces to couple energy from said anode circuit to said cavity for establishing a standing electromagnetic wave therein, and radio frequency output coupling means for extracting energy from said cavity comprising a coaxial connector mounted in said magnet structure including an inductive loop having a substantial length thereof extending in close proximity to the interior surface of said cavity and the inner end supported by said insulative member and conducf tively coupled to said anode contact for supporting said loop in said cavity and for effecting tight coupling to said tube and cavity.

8. Radio frequency apparatus comprising a magnetron structure defining a radio frequency cavity and having a pair of opposed pole pieces defining a gap in said cavity, said pole pieces being predeterminedly adjustively positioned and thereby determining the conguration of the magnetic field in said gap, a magnetron tube including an envelope containing an interdigital anode circuit and carrying an axially spaced pair of external anode contacts, an insulative member extending transversely across said cavity and fixedly supporting said tube in said gap in spaced relation to said pole pieces, means including bowed low inductance externally conductive straps interconnecting each said anode contacts and an adjacent pole piece for enabling relative adjustive movements of said pole pieces, completing a radio frequency circuit with said magnet structure for resonating said cavity and providing substantial thermal paths from said tube to said magnet structure, and radio frequency output coupling means comprising a coaxial connector mounted in said magnet structure including an inductive loop having a substantial length thereof conforming generally to the inner wall of said cavity and extending in close proximity thereto, said loop having the inner end thereof supported by said insulative member and conductively coupled to one of said anode contacts, whereby said coupling means is adapted for effecting tight coupling to said tube and cavity.

9. Radio frequency apparatus comprising a magnet structure defining a radio frequency cavity and having a pair of opposed pole pieces defining a gap in said cavity, a magnetron tube mounted in said gap in generally coaxial relation with the magnetic field therein and including an anode circuit and an axially spaced pair of annular external contacts, means coupling energy from said tube to said cavity through resonating same, and output coupling means comprising a coaxial connector, a pair of a parallel planar conductors spaced by an interposed dielectric element and each being connected with one of the coaxial conductors of said coaxial connector and having a portion apertured and making circumferential electrical contact with one of said anode contacts.

10. Radio frequency apparatus comprising a magnet structure defining a radio frequency cavity and having a pair of opposed pole pieces defining a gap in said cavity, a magnetron tube including an envelope containing an anode circuit and having an axially spaced pair of external anode contacts, an insulative member extending transversely across said cavity and supporting said tube in said gap, means coupling energy from said tube to said cavity for resonating same, and radio frequency output coupling means comprising a coaxial connector carried by said magnetron structure and a line-overground plane transmission line connecting each said anode contacts with a conductor of said coaxial connector and with said insulative member interposed between and effectively spacing the conductors of said transmission line.

11. Radio frequency apparatus according to claimv 10, wherein said support member includes an electrically insulative high thermal conductivity element immediately surrounding said tube intermediate said anode contacts.

12. Radio frequency apparatus comprising a magnet structure defining a radio frequency cavity and having a pair of opposed pole pieces defining a gap in said cavity, said pole pieces being predeterminedly adjustively positioned and thereby determining the conguration of the magnetic field in said gap, a magnetron tube including an envelope containing an interdigital anode circuit and carrying an axially-spaced pair of annular external anode contacts, an insulative member extending transversely across said cavity and iixedly supporting said tube in said gap in spaced relation to said pole pieces, radio frequency output coupling means comprising a coaxial connector mounted in a Wall of said cavity and having connected to the inner and outer conductors thereof one of a pair of planar conductors extending in said cavity on opposite sides of said insulative member and thereby spaced, said planar conductors constituting a line-overground plane transmission line and each planar conductor having an apertured portion making circumferential electrical contact with one of said anode contacts, and means including bowed low-inductance thermally conductive straps interconnecting each said planar conductors adjacent said anode contact and an adjacent pole piecey for enabling relative adjustive movements of said pole pieces, completing a radio frequency circuit with said magnet structure for resonating said cavity and providing substantial thermal paths from said tube to said magnet structure.

13. For use in a magnetron type radio frequency device having a predetermined output RF. frequency, radio frequency attenuator comprising in combination, an elongated member of non-magnetic resistive electrical lossiness, a spiral groove in the outer surface of said member and a bared conductor Wound in said groove, said groove and the section of said conductor therein having lineal dimensions corresponding to the Wavelength of said predetermined radio frequency to be removed from said conductor, the depth of said groove being greater than the diameter of said conductor, whereby said conductor is substantially imbedded in said member for maximum coupling.

14. A radio frequency attenuator according to claim 13, wherein said member comprises a porous ceramic having a conductive material uniformly distributed therethrough.

References Cited by the Examiner UNITED STATES PATENTS 1,676,869 7/1928 Richter 338--303 X 2,142,345 l/1939 Braden 315--39 X 2,490,008 11/ 1949 Shulman 315-39 X 2,624,865 1/1953 Nichols 315-39.51 X 2,774,046 12/ 1956 Arditi et al. 333-84 2,973,455 2/1961 Marlowe S15- 39.63 X 3,017,544 1/1962 Kane et al 317-158 3,020,446 2/ 1962 Bessarab 315-3971 3,034,014 5/1962 Dreyler 315-3977 3,127,538 3/1964 Dench 315--3.5 X

GEORGE N. WESTBY, Examiner.

HERMAN KARL SAALBACH, Primary Examiner. 

1. RADIO FREQUENCY APPARATUS COMPRISING A MAGNET STRUCTURE INCLUDING A PAIR OF OPPOSED SPACED POLE PIECES DEFINING A GAP, SUPPORTING MEANS SUPPORTING SAID POLE PIECES FOR ANGULARLY ADJUSTMENT TO VARY THE CONFIGURATION OF THE MAGNETIC FIELD IN SAID GAP, RETAINING MEANS CARRIED BY SAID MAGNET STRUCTURE SUPPORTING AN ELECTRIC DISCHARGE DEVICE IN A FIXED POSITION IN SAID GAP, SAID DEVICE INCLUDING AT LEAST ONE EXTERNAL CONTACT MEMBER, AND MEANS INCLUDING AT LEAST ONE FLEXIBLE CONDUCTIVE ELEMENT INTERCONNECTING SAID CONTACT MEMBER AND ONE OF SAID POLE PIECES TO COMPENSATE AN R.F. CIRCUIT THEREBETWEEN. 